The US television networks have agreed to censor themselves when broadcasting Osama bin Laden's publicity videos, in response to a request from an administration increasingly anxious that it is losing the propaganda war.

In an unprecedented accord, the five major networks, CNN, NBC, ABC, CBS and Fox News Channel, said they would limit their coverage of Bin Laden's videos after a conference call on Wednesday with the national security adviser, Condoleezza Rice.

In the past week, Bin Laden's al-Qaida organisation delivered two videos to the Kabul office of the Qatar-based Arabic news channel, al-Jazeera, which were relayed live by the US networks. In both videos, there are appeals, made by Bin Laden or his lieutenants, for Muslims to rise up against US targets across the world.

Dr Rice expressed concern that apart from the clear appeals for violence, the videos could include coded messages aimed at al-Qaida cells around the world.

The networks have agreed to avoid broadcasting any future videos directly, and would only quote passages which did not include rhetoric urging violence against Americans. They also agreed to stop the broadcast of repeated excerpts from the tapes.

In a statement, CNN said it would not air any of Bin Laden's addresses live and promised to "consider guidance from appropriate authorities" in deciding what to broadcast.

Rupert Murdoch, the Australian-born media magnate who owns Fox News and News International, said his TV operations would censor themselves if it was thought they were being used to spread coded messages or propaganda from Bin Laden and his al-Qaida network.

"We'll do whatever is our patriotic duty," said Mr Murdoch, now a US citizen, after News Corp's annual general meeting in Adelaide, the birthplace of his media empire.

The price of security for people in democracies, he predicted, would be "a major diminution of civil liberties" during this "period of unpredictable but protracted terrorism within our borders".

However, he told his Australian shareholders that the war on terrorism also brought opportunities for his network. The 70-year-old tycoon said that although the September 11 attack had hit short-term advertising revenues and raised newsgathering costs, he hoped the conflict in Afghanistan could raise viewers' "consciousness" of his 24-hour Fox News operation in the way that the Gulf war was the making of CNN.

The network chiefs said they had not been convinced by the White House argument that the videos may be used to convey coded messages. Whatever such hidden messages might be in the tapes would get out anyway through transcripts of the tapes on the internet, network executives have argued.

Instead, they said the accord sprang from a realisation of the new and unique nature of the terrorist threat.

"This is a new situation, a new war and a new kind of enemy," Andrew Heyward, the president of CBS News, told the New York Times. "Given the historic events we're enmeshed in, it's appropriate to explore new ways of fulfilling our responsibilities to the public."

The Bush administration is concerned that the videos issued by Bin Laden have had their desired effect of galvanising Arab support for his cause, by identifying his actions with the suffering of the Palestinians and Iraqis.

The White House is also worried about the impact of reports of civilian casualties from US bombings.

US press outlets have been under pressure to reduce the amount of detail in their war reporting in the interests of national security, especially when the reports involved the activities of special forces.

Angry at leaks of US military preparations, President Bush has issued a warning to his staff to be careful what they say to the press and avoid journalists if possible.

In an article on Newsweek magazine's online edition, a columnist, Martha Brant, said she was told by one administration source: "Remember, if you run into me somewhere, make sure you stick out your hand and introduce yourself. In other words, act like we never met."